The present invention relates to a flexible tube for an endoscope.
In general, an endoscope includes a flexible tube which is inserted into a human cavity, and the flexible tube includes a spirally-wound metal tube, a reticulated tube and a flexible sheath. The spirally-wound metal tube is covered with the reticulated tube, and further the reticulated tube is covered with the flexible sheath.
There may be a case where the spirally-wound metal tube undesirably shrinks by autoclaving which is performed after use of the endoscope. Therefore, it is desirable to enhance durability of the flexible tube against autoclaving. Japanese Patent Provisional Publication No. HEI 9-24020° A. discloses a flexible tube for an endoscope. The flexible tube in this publication uses a framed structure unit configured such that a plurality of joint members each of which has a form of a short cylinder are coupled to each other with rivets, in place of the spirally-wound metal tube. By this structure, durability with respect to autoclaving can be enhanced.
However, the flexible tube disclosed in HEI 9-24020A has a drawback that a twisting response, representing rotating motion of a tip portion of the flexible tube in response to an operation to rotate a proximal portion of the flexible tube about an axis line, and resilience, representing motion of the flexible tube getting back to a straightened state after being bent by an external force, are less than those of the flexible tube employing the spirally-wound metal tube. Therefore, usability of the flexible tube having the framed structure unit may be less than that of the flexible tube employing the spirally-wound metal tube.